Information on malnutrition for school-age children and adolescents (5-19 years) in South Asia is fragmented and inconsistent, which limits the prioritization of nutrition policies, programmes and research for this age group. This scoping review aimed to synthesize existing evidence on the burden of malnutrition for children and adolescents aged 5-19 years in South Asia, and on interventions to improve their nutritional status. Cochrane Library, EMBASE, Medline and Google Scholar were systematically searched for articles published between January 2016 and November 2022. Eligible studies reported the prevalence of undernutrition, overweight/obesity, micronutrient deficiencies and unhealthy dietary intakes, and interventions that aimed to address these in South Asia. In total, 296 articles met our inclusion criteria. Evidence revealed widespread, yet heterogeneous, prevalence of undernutrition among South Asian children and adolescents: thinness (1.9%-88.8%), wasting (3%-48%), underweight (9.5%-84.4%) and stunting (3.7%-71.7%). A triple burden of malnutrition was evident: the prevalence of overweight and obesity ranged from 0.2% to 73% and 0% to 38% (with rapidly rising trends), respectively, alongside persistent micronutrient deficiencies. Diets often failed to meet nutritional requirements and high levels of fast-food consumption were reported. Education, fortification, supplementation and school feeding programmes demonstrated beneficial effects on nutritional status. Comprehensive and regular monitoring of all forms of malnutrition among children and adolescents, across all countries in South Asia is required. Further, more large-scale intervention research is needed to ensure policy and programmes effectively target and address malnutrition among children and adolescents in South Asia.